1. Field of the Invention
The present invention relates to an apparatus and a method for automatically mounting electronic parts in which electronic parts are taken out from a parts feeding section by means of an holding nozzle provided in a nozzle head and are then mounted on a printed substrate.
2. Description of the Related Art
Heretofore, for continuously and automatically mounting electronic parts on a printed substrate during manufacturing processes, chip-like electronic parts being fed one by one by a parts feeding device or the like are picked up by a holding nozzle using a vacuum pump or a magnet and are then mounted at predetermined positions on the printed substrate. Among such type of automatic electronic parts mounting apparatuses, there is known one having a function of detecting the picked up state of the parts for accurately mounting the parts on the printed substrate.
Such a type of apparatus for automatically mounting electronic parts is disclosed in Japanese Utility Model Laid Open No. Sho 60-121671, in which an orientation of an electronic part being picked up by a holding nozzle is judged as correct when a light beam from a light-emitting element is detected by a light-receiving element. When the thickness of a part varies depending on its type, the height of the light-emitting and light-receiving elements is adjusted by rotating a driving lever in accordance with the thickness information of the parts, so as to make correct judgment of the part's orientation and shape.
According to the aforementioned conventional apparatus, the abnormality of orientation can be detected when the picking up is carried out by an unexpected or incorrect surface of an electronic part. For example, if the picking up is done while the part is in a completely upright state, the incorrect orientation can be detected since the light beam from the light-emitting element is interrupted by the electronic part. On the other hand, however, if the electronic part 100 is held to the take-out nozzle 101 in an inclined state, as shown in FIG. 1, so that the light beam from the light-emitting element passes a point A in FIG. 1 in the direction perpendicular to the sheet, the light beam cannot be interrupted by the electronic part 100. As a result, it would erroneously be judged that the electronic part 100 has correctly been picked up as shown by the two-dot chain line, so as to then be mounted on the printed substrate in the orientation as shown by solid lines. Due to this mislocation of the parts, the substrate would become defective.